The invention concerns a method for the thermal processing of product pieces produced from old tires, which consist of a material compound, which comprises at least one material component which decomposes by heating, the processing occurring by mechanically moving and/or fluidizing the product pieces in a device and by heating the product pieces to a material decomposition temperature via heated contact surfaces of the device, at which temperature the material compound decomposes into one or several solid matter material components and fluids, which can be taken out of the device separately.
Such a processing became known by the U.S. Pat. No. 4,084,521. First, the old tires are cut into pieces, which are then dried. Then the pieces enter a reaction container in which they are heated to the material decomposition temperature during transport from entrance to exit. The reaction container is at subatmospheric pressure and sealed air-tight. The gases developing during the decomposition and the pieces not decomposed then enter a chamber, where they are separately carried off.
A method for the processing of old tires and similar materials is described in the U.S. Pat. No. 4,240,587. The associated device includes an installation for cooling tires of different sizes to a temperature where the rubber becomes brittle, such that a first part of recoverable rubber can be separated. The device is essentially operated with the re-usable by-products of the pyrolytic reduction of the tires, where hydrocarbons, heated gas and other commercially recoverable by-products form.
DE 40 34 985 teaches a method for the controlled low temperature degassing of pre-comminuted organic substances, preferably of old tires, plastics and biomass, with the emphasis on the recovery of fuel and raw materials by an electrically heated conveyor belt. DE 196 17 450 concerns a method and a device for the recovery of elastomers from waste material. For this purpose the waste material is introduced into an upstream chamber through a first lock for drying, when dried it is transferred in a retort chamber with reduced oxygen partial pressure and in there heated for dry distillation. The liquid distillate and the dry residue are drawn off. The residue enters a downstream chamber for the comminution and pulverization. Residue not pulverized or residue similar to granulates are carried out through a second lock.
The mechanical processing of vehicle tires which cannot be used anymore has become known, for example, by the DE 44 16 155 A1.
It became known that large wear occurs in rough comminution machines and in mills and that additionally the amount of throughput per unit of time is limited if old tires are fed into comminution machines. After the comminution or the milling, a material mixture from numerous components exists which have to be separated if a sensible reuse/recycling is intended. A separation is not possible for larger granulates because the individual granulates consist of an intimate material compound, which cannot be undone by simple means. That means that granulates in the most different material compositions can only be separated into individual material compounds via chemical processing.
In the chemical processing according to the state of the art, old tires or parts of old tires are processed by pyrolysis and/or depolymerization.
In the thermal processing of old tires, the heated and processed product pieces can adhere to or cake to the device inner walls and/or the mixing tools of the device provided for that purpose.
Therefore, the object of the invention is to further develop the known methods such that no such conglutinations can occur.
For the solution of the object it is proposed according to the invention, to discontinually operate the device in the thermal processing of old tires and to introduce the product pieces into a material pre-placement containing soot in the device inner space. The product pieces are powdered with soot and cannot permanently adhere to or cake to the device inner wall and/or the mixing tools.
One half of the starting material of the fed product pieces can be converted into gases and oil vapors. The other half of the treated starting material can be separated into low-value soot (carbon, sulfur) and steel wires. The developing gases can be used for generating energy. The condensed, relatively homogeneous oil can be further used as raw material. The soot comprising a high carbon content can be used for generating energy due to its calorific value. The steel salvaged from the vehicle tires can be again integrated into a product cycle as raw material.
The material pre-placement can consist of material components, which develop during the decomposition of the material compound of the product pieces. The fed starting material is, for example, mixed with the still warm soot in this embodiment. The device is not cooled down too much. The starting material is pre-heated by being in contact with the soot.
In a preferred development of the invention, the separation of the individual material components is obtained by heating up of the product pieces to a temperature of up to T=500xc2x0 C.
The efficiency of the method can be improved in that the thermal processing of the product pieces occurs under vacuum.
The purity of the generated end products can be improved if the thermal processing of the product pieces occurs under exclusion of oxygen.
For the application of the processing, a device is used according to the invention, which comprises installations and surfaces for the mechanical fluidization and/or movement and thermal treatment of product pieces provided in a device inner space, which product pieces are produced from old tires, for example from vehicles, by comminuting the old tires, where the product pieces consist of a material compound, which comprises at least one material component which decomposes by heating, with product contact surfaces of the device which can be heated up for the heating of the product pieces to a material decomposition temperature, with a connection or connections of the device for maintaining a vacuum in the device inner space, with a connection or connections of the device for feeding the product pieces into the device inner space, with a connection or connections of the device for feeding a gas into the product inner space and with a connection or connections of the device for the carrying off of a fluid or fluids and a solid material component or of solid material components, which result from the thermal treatment of the product pieces.
For example, the product pieces can be heated up to a temperature of up to T=500xc2x0 C. by contact heating via the device inner walls.
The mixing and comminution of the product pieces can be achieved by installations of the device, which are designed displaceably in a stationary housing of the device.
The installations of mixing elements can be disposed on a rotatable shaft in a variant of the device, which shaft runs on bearings at the ends of the device, where the shaft passes through the device and the mixing elements pass over the heated surfaces of the device.
It is clear that the above mentioned method and the corresponding device can also be used for the processing of thermally decomposable rubber and/or plastic waste from the production of vehicles.
Additional distinctions and advantages of the invention can be gathered from the description of an embodiment of the invention, the drawing, which shows details relevant to the invention, and from the claims. The individual characteristics can be realized each individually or collectively in any combination in an embodiment of the invention.